The present invention generally relates to an electrophotographic copying machine and, more particularly, to a system for detecting a trouble occurring in a scanning mechanism which is used in the electrophotographic copying machine to enable a document or original to be optically scanned.
In currently utilized electrophotographic copying machines, an image of the document or original to be reproduced is transferred to an electrophotosensitive member by means of an optical transfer system. The optical transfer system generally comprises an illuminator including an electric lamp for illuminating the original imagewise which is then placed on a transparent support plate, and an optical path for directing the light which carries the image of the original and which has been reflected from the original, towards the electrophotosensitive member. Depending on the manner by which the original is illuminated, the currently utilized electrophotographic copying machines can be classified into two types; one type wherein the transparent support plate is moved together with the original thereon relative to the illuminator and the other type wherein the illuminator is moved relative to the transparent support plate.
In either type of the electrophotographic copying machines, a scanning mechanism including an electrically operated motor and a drive transmission device for transmitting the drive of the motor to the illuminator or the transparent support plate is essentially employed in order to enable the illuminator to scan the original imagewise. It often happens that, when any abnormal condition occurs in the scanning mechanism while the other parts of the electrophotographic copying machine function satisfactorily, the transparent support plate or the illuminator will not move properly while the lamp remains lit. In the worst it may happen, this may result in excessive heating of a local area of the transparent support plate to such a temperature as may cause an operator of the machine to suffer from a burn when to touch the transparent support plate or as may cause the cracking or breakage of the transparent support plate which is generally constituted by a transparent plate glass. In particular, the longer the time during which the lamp remains lit without being turned off simultaneously with the failure of the scanning mechanism to operate, the higher the possibility of these calamities.
In general, the failure of the scanning mechanism to operate properly may be considered as attributable to either a breakdown of the drive motor or a breakdown of the drive transmission mechanism even though the drive motor is satisfactorily functioning. However, in order to avoid the occurrence of one or all of the calamities described above, it is necessary to detect the occurrence of the abnormal condition irrespective of the cause of the failure of the scanning mechanism to operate properly, substantially simultaneously with or immediately after the occurrence of such abnormal condition.
Unfortunately, none of the currently utilized electrophotograhic copying machines is equipped with any trouble detecting system designed particularly for detecting the breakdown occurring in the scanning mechanism. Although the breakdown of the drive motor of the scanning mechanism used in the prior art electrophotographic copying machines can readily be detected by ascertaining that no other electrically operated parts of the copying machine to be suquentially operated subsequent to the start of operation of the drive motor of the scanning mechanism operate, no breakdown of the scanning mechanism can readily be detected for a prolonged period of time before the sequence of operation of various movable parts of the copying machine shows an abnormal condition occurring in the scanning mechanism. This prolonged period of time would be such an extent as to result in one or all of the calamities due to the excessive heating of the local area of the transparent support plate in the manner described above.